The present disclosure relates to a control device, and more specifically to a control device of a disk storage device.
It is known that a magnetic disk device performs a retraction operation that retracts a magnetic head from over a magnetic disk when power is shut down. Regarding a technique that controls the retraction operation, for example, Japanese Unexamined Patent Application Publication No. 2002-298530 (Patent Document 1) discloses a configuration in which when a head reaches a predetermined retraction switching position 403, the head is moved to a ramp 16 by using charges accumulated in a retraction capacitor.
Further, Japanese Unexamined Patent Application Publication No. 2004-178790 (Patent Document 2) discloses a configuration in which when power is shut down, a head 16 is unloaded to a ramp 20 by constant voltage driving after the head 16 is caused to reach an inner stopper that is a predetermined position opposite to the ramp 20.
Japanese Unexamined Patent Application Publication No. 2011-248965 (Patent Document 3) discloses a configuration which alternately performs an operation to apply a drive voltage to a voice coil motor VCM and an operation to detect a back electromotive voltage (BEMF) generated in the VCM and sets a value of the drive voltage applied to the VCM according to a magnitude relation between a threshold voltage Vref and the BEMF.